The present invention relates to road surface marking tape for temporary use in marking out temporary traffic diversions and comprising a base layer of nonvulcanized or non-cured soft elastomeric material and a reinforcing material embedded in the base layer. The present invention also relates to a method marking road surfaces with the aid of such tape.
It is known to use to mark the surfaces of roads, highways, etc., with a foil material which is based on a polymeric base layer, for instance a resin, thermoplastic, thermoelastomeric or rubber material, that includes a heavily light-reflecting layer which includes pigments, colorants, and/or glass beads embedded either in the base layer or in an upper layer adjacent said base layer, or in both of said layers. Such materials are described, for instance, in U.S. Pat. Nos. 2,440,584, 3,764,455, 3,915,771, 4,117,192, 4,248,932, 4,282,281 and 4,299,874, and also in EP-A 614503 and SE-B 458215. A common feature of all of the known materials described in said publications is that they are intended for permanent use and are thus designed and adapted for such use. The most important properties required of such road surface marking foils lie in their high mechanical strength, i.e. high wear strength, high abrasive resistance with respect to their reflective layers, a long useful life, etc. The base layer has therefore been designed to meet these requirements. As a result such road surface marking foils are relatively rigid and will have certain drawbacks with respect to compatibility and conformity to the state of the road surface on which they are laid, and also with respect to their ability to effectively adhere to and lie in tight abutment with said surface, even when a soft polymeric material is used. Consequently, it is preferable in the majority of cases, at least in normal outdoor temperatures in a temperate climate, to apply a primary layer consisting of a rubber solution or the like prior to applying the foil to the road surface. Such road surface marking materials are unsuitable for applications where only a temporary marking is required, for instance over a time period of up to 10-12 months, for a number of reasons. Such materials are not easily removed without leaving any trace, due to the use of the primer. The primer is absolutely necessary in achieving effective adhesion, since the marking material is relatively thick and thus also relatively stiff and difficult to xe2x80x9cmoldxe2x80x9d to the irregularities of the road surface, as inferred above. These materials are also highly expensive and are discarded as waste when their use is fulfilled. The waste material is also difficult to handle in a manner that is environmentally acceptable.
There is thus a need to be able to use foil-type road-surface marking material, hereinafter called road marking tape, also for temporary purposes instead of needing to use less effective and less traffic-safe markings with loose or firmly mounted cones or other similar xe2x80x9cmechanicalxe2x80x9d solutions, or by painting directly on the road surface, such painted markings being difficult to erase when no longer required. Although various types of temporary road-marking materials based on metal foil, for instance aluminium foil, are now commercially available, these materials are relatively expensive and do not have sufficient strength and wear resistance. The removal of such materials from a road surface also presents serious problems when said materials have been applied to said surface with the aid of a strong adhesive.
Road-surface marking tape of the kind defined in the introduction and primarily intended for temporary use in diverting road traffic is described in EP-A 0304405. The tape contains a very soft and formable non-cured elastomer based on acrylnitrile-butadiene which forms a base layer having a thickness of about 0.5 mm. This layer is much thinner than corresponding layers of earlier used permanent tapes and is therefore considered to have properties which enable the tape to be laid directly on the road surface with good adhesion and conformity with respect to irregularities in the road surface. However, the preferred embodiments include an adhesive layer on the undersurface of the tape for effective adhesion of the tape to said surface, such adhesive layers probably being always used in practice. The base layer contains both pigments and glass beads which provide the tape with the desired optical reflective properties. The base layer is reinforced with a strengthening layer which is embedded at least partially into the elastomeric base layer, in order to facilitate handling of the tape in practice on the one hand and, on the other hand, to impart to the tape the mechanical strength properties required when laying-out the tape, such as high tensile strength and appropriate ultimate tensile strength so that tape can be torn away from said road surface when necessary. The reinforcing layer is said to have the form of a plastic, metal or fabric net, preferably with square or rectangular meshes. According to the main Claim of said patent publication, it is necessary for the reinforcing layer to be embedded at least partially in the base layer.
Although the reinforcing layer solves certain strength problems, primarily with respect to removing the tapexe2x80x94which is done manuallyxe2x80x94by tearing up the tape piece-by-piece until all of the tape has been removed, it creates other problems relating to the ability to mold the base layer to irregularities in the road surface and therewith enable the tape to be placed in tight abutment with said surface for effective and durable adhesion thereto. Thus, although without being specifically mentioned, the reinforcement has on the base layer a mechanically stiffening effect that reduces the mouldability or shaping ability of the tape and therewith deleteriously affects the conditions required to achieve effective adhesion and sealing of the tape to said road surface. The reinforcement also means that the tape cannot be readily handled after its removal and presents a problem with regard to carrying the used tape away as scrap and also with regard to recycling or reusing the material. Because the reinforcing net reduces the pliability of the road marking tape for temporary use, it is often preferred to use a primary coating to facilitate adhesion of the tape. This solution, however, is encumbered with other drawbacks, such as extra costs entailed by material, solvent, manufacture and placement, additional work involved when laying-out and removing the tape, and increased environmental problems due to the requirement of a solvent.
The object of the present invention is to provide a road surface marking tape for temporary use which is based on a base layer of non-cured or non-vulcanized soft elastomeric material and a reinforcing material which imparts to the base layer, and therewith to the tape as a whole, a firmness and tensile strength sufficient to facilitate handling of the tape, and to a method of laying-out and removing such tape while avoiding the drawbacks described in the introduction. To this end, the inventive marking tape is characterised by the characteristic features set forth in respective product Claims, while the inventive method is characterised by the method steps set forth in respective method Claims.
The inventive marking tape thus includes a base layer of soft, non-vulcanized or non-cured elastomeric material, and a reinforcing material embedded therein, said reinforcing material comprising short non-metallic fibres distributed essentially uniformly in the base layer.
The short fibres are present in an amount corresponding to 5-50% of the weight of the base layer. By xe2x80x9cshortxe2x80x9d fibres is meant in this case primarily the opposite of xe2x80x9clongxe2x80x9d fibres and suitably a fibre length that corresponds to the thickness of the base layer or shorter than said thickness. With respect to the amount of fibres present in the reinforcing layer, the lower limit of 5% represents a limit at which the base layer, and therewith the tape as a whole, will have insufficient tensile strength and/or an excessively high rupture strain and thus having the behaviour of a viscous chewing gum-like material that is difficult to stretch and almost impossible to handle when laying-out the tape. The upper limit of 50% with respect to fibre content provides a base layer which can be handled relatively well and which is acceptably pliable at least at such high outdoor temperatures as those experienced in tropical regions. A fibre content above this upper limit, however, will greatly impair the suppleness, i.e. shapability, of the tape such that the tape can no longer be used as a road surface marking tape. The reinforcing material will preferably comprise fibres that have lengths generally between 0.5 and 5 mm, preferably between 1 and 3 mm, which has been found to provide an optimal compromise between different tape properties. The material will preferably comprise textile fibres, plastic fibres or carbon fibres. Textile fibres are preferred in most cases. A tape that has optimum strength properties when used in normal outdoor temperatures in a temperate climate is obtained when the fibres are present in an amount corresponding to 10-20% of the weight of the base layer.
The elastomeric material is suitably a non-vulcanized synthetic rubber of the acrylnitrile-butadiene type.
According to the inventive method of providing road surfaces with a temporary marking or signalising system with the aid of an inventive tape, the tape is unwound continuously from a tape roll with the aid of an appropriate mechanical tape-laying device. When the tape is to be removed at the end of said temporary period, the tape is frozen to a brittle state and disintegrated mechanically to powder form or to fragmentary state, and then swept up or removed in some other way. The steps of freezing the tape so that it disintegrates and the step of removing the disintegrated powdery material are both effected mechanically, preferably essentially at one and the same time in a single step. The frozen tape is disintegrated with the aid of a rotary steel brush or some corresponding device, and the powder, or fragments, are removed by suction.